The Collaborative International Dictionary of English v.0.48:

Orchis \Or"chis\, prop. n.; pl. Orchises. [L., fr. Gr. ? a
   testicle, the orchis; -- so called from its tubers.]
   [1913 Webster]
   1. (Bot.) A genus of endogenous plants growing in the North
      Temperate zone, and consisting of about eighty species.
      They are perennial herbs growing from a tuber (beside
      which is usually found the last year's tuber also), and
      are valued for their showy flowers. See Orchidaceous.
      [1913 Webster]

   2. (Bot.) Any plant of the same family with the orchis; an
      orchid.
      [1913 Webster]

   Note: The common names, such as bee orchis, fly orchis,
         butterfly orchis, etc., allude to the peculiar form
         of the flower.
         [1913 Webster]

WordNet (r) 3.0 (2006):

butterfly orchis
    n 1: Mexican epiphytic orchid having pale green or yellow-green
         flowers with white purple-veined lip [syn: butterfly
         orchid, butterfly orchis, Epidendrum venosum,
         Encyclia venosa]
    2: Mediterranean orchid having usually purple flowers with a
       fan-shaped spotted or striped rose-red lip [syn: butterfly
       orchid, butterfly orchis, Orchis papilionaceae]